The boiler is a 4 year old Worcester Bosch installed by British Gas, we have 8 rads 3 newish and 5 quite old (20 years).
So I take it is a Combi or sytem boiler in which case there should be no issues. Do you know the whether its a 24kw or 30kw. I take it BG power flushed the system and balanced all the rads after fitting it?
Have you bled the radiators?
Do you have Thermostic radiator valves?